At least 161 people have died and more than 1,400 were injured across Turkey after members of the military attempted a coup, blocking traffic on bridges over the Bosphorus in Istanbul and issuing a declaration of martial law.

The term “parallels” is used by the Turkish government in reference to the followers of Fethullah Gülen, a Sunni cleric who has lived in self-imposed exile in Pennsylvania since 1999. Once an ally, Mr. Erdogan now says the influence of Mr. Gülen as akin to that of a “parallel state”, and has accused him of plotting coups from his 26-acre compound in the Poconos.

As someone who suffered under multiple military coups during the past five decades, it is especially insulting to be accused of having any link to such an attempt. I categorically deny such accusations....

Government should be won through a process of free and fair elections, not force," he said. "I pray to God for Turkey, for Turkish citizens, and for all those currently in Turkey that this situation is resolved peacefully and quickly."

Gülen exercises tremendous moral and political influence in Turkey, presiding over a movement that blends conservative Muslim values with a cosmopolitan lifestyle. His adherents are rumored to hold sway in the judiciary and national police.

“The assertion that the TNP [Turkish National Police] is controlled by Gulenists is impossible to confirm but we have found no one who disputes it,” wrote James Jeffrey, then-US ambassador to Turkey in 2009, “and we have heard accounts that TNP applicants who stay at Gulenist pensions are provided the answers in advance to the TNP entrance exam.”

Gülen first attracted a following the 1960s and 1970s, preaching a version of Islam that promoted democracy, interfaith dialogue and secularized education – particularly science, math and technology – as a credit to the country, one which did not conflict with his adherents’ obligations as Muslims.

His supporters run lobbying groups, Turkish cultural centers and think tanks in global power centers such as Washington and Brussel, Newsweek wrote in 2009, and own hospitals, banks, universities and newspapers and TV networks in Turkey and elsewhere. They also operate a global network of schools that number in the thousands, including about 120 charter schools in the United States, with a focus on recruiting underprivileged children.

Erdogan, an Islamist who has nonetheless given inspired arguments in favor of the secular character of Turkey’s political system, has tried battling Gülen in US courts. One human rights case thrown out in June by a Pennsylvania district court judge charged that the cleric had ordered allies of his movement in the Turkish judiciary and police to target members of a rival spiritual movement.

And as the Atlantic noted in 2014, Gülen’s charter schools in Ohio have come under scrutiny for allegations ranging from cheating on tests to overcrowding and sexual misconduct. In April of that year, the FBI raided the headquarters of several Gülen’s academies in the Midwest, apparently on suspicion of misuse of federal funds.

According to a 2015 book by former journalist and professor at the Centre for Turkey Studies Natalie Martin, President Erdogan and Gülen were once allies, with the latter contributing money and urging his followers to vote for Erdogan’s Justice and Development Party (AKP) in its 2001-2002 rise to power. Both wanted to see the military, which has intervened several times in Turkey’s history, take a less prominent role in the country’s affairs. But cracks developed in recent years, finding major expression in 2013, when Erdogan’s government closed thousands of Gülenist schools. That same year, Erdogan accused the cleric of orchestrating a massive corruption scandal involving key AKP members.

On Saturday, the BBC reported that the government had begun a purge of Gülenist members from the police, military, and civil service, and Turkey's Prime Minister Binali Yildirim said that the government may even consider reinstating the death penalty in the wake of the coup.

US Secretary of State John Kerry told reporters Saturday that the US would consider an extradition request from Turkey for Gülen if the Erdogan administration were to "present us with any legitimate evidence" of wrongdoing.